This demonstrates how to implement a virtual stack class.
'This is a virtual stack class
Public Class VStack
Dim cStackItems As New Collection()
Dim iItemCount As Int32 ' The size of the stack (-1 = dynamic size, 0 = empty)
Public Sub New()
iItemCount = -1 ' This stack will be dynamic
End Sub
Public Sub New(ByVal iSize As Int32)
iItemCount = iSize
End Sub
'Public Sub New(ByVal iSize As Int32, ByVal oTemplate As Object)
' iItemCount = iSize
' ' Put template in all items
' Dim i As Int32
' For i = 0 To iItemCount - 1
' cStackItems.Add(oTemplate)
' Next
'End Sub
Public Sub Push(ByVal oItem As Object)
If cStackItems.Count < iItemCount Or iItemCount = -1 Then
cStackItems.Add(oItem)
ElseIf cStackItems.Count = iItemCount Then
Throw New OverflowException("Not enough room on the virtual stack.")
End If
End Sub
Public Function Pop() As Object
Dim oTemporaryItem As Object
Try
oTemporaryItem = GetItem()
cStackItems.Remove(cStackItems.Count) ' delete the last item
Return oTemporaryItem
Catch e As IndexOutOfRangeException
Throw e
Catch e As Exception
Throw e
End Try
End Function
Public Function Peek() As Object ' Like a pop, but doesn't delete the item
Dim oTemporaryItem As Object
Try
oTemporaryItem = GetItem()
Return oTemporaryItem
Catch e As IndexOutOfRangeException
Throw e
Catch e As Exception
Throw e
End Try
End Function
Public Function GetItem() As Object
If cStackItems.Count >= 1 Then
Return cStackItems.Item(cStackItems.Count) ' get the most recent item
Else
Throw New IndexOutOfRangeException("No items on the stack.")
End If
End Function
Public ReadOnly Property CurrentSize() As Int32
Get
Return cStackItems.Count
End Get
End Property
Public ReadOnly Property MaxItems() As Int32
Get
Return iItemCount
End Get
End Property
End Class
-Daniel Okely Inaugural Developerfusion.com Prize Winner
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